This study is a randomized, open-label, crossover design to obtain the pharmacokinetic parameters of serum testosterone from two formulations of testosterone transdermal systems in order to determine their relative bioavailability. Testoderm Testosterone Transdermal System and Testoderm- II Testosterone Traansdermal System are the comparison systems. In addition, the dose relationship of one and two Testoderm-II systems will be evaluated. Dihydrotestosterone, estradiol and free testosterone will also be described for each application of the four treatments in 18 hypogonadal male patients. The objectives of this study are: (1) Estimate the bioavailabitily of Testoderm-II (application on hip) using Testoderm Testosterone Transdermal System (scrotal application) as the reference. (2) Evaluate topical reactions of Testoderm II. (3) Evaluate the dose relationship of one and two Testoderm-II, (60 and 120 cm2).